The present invention relates to a pneumatic tire, more particularly to a heavy duty tire provided with a five-rib tread pattern.
In a pneumatic tire for heavy duty vehicles such as tractor head, trailer and the like, the most widely adopted are five-rib tread patterns.
In such a five-rib tread pattern, usually the ground pressure of a center rib becomes high and the rigidity of axially outermost shoulder ribs is large. Therefore, there is a tendency that the ground pressure of middle ribs positioned between the center rib and shoulder ribs becomes uneven, and moreover the uneven ground pressure distribution is varied during running and also by the service conditions. As a result, so called rib punching wear—a phenomenon such that the middle ribs rapidly wear more than the center rib and shoulder ribs—is liable to occur. Especially, in the case that the middle ribs are provided with sipes for improving wet performance, rib punching wear is liable to begin at the sipes.